vendredi 14 avril 2017

The three International Space Station residents upgraded computer hardware and software today. The crew is also heading into the weekend preparing for the arrival of a new crew and a new cargo shipment.

Commander Peggy Whitson and Flight Engineer Thomas Pesquet replaced outdated routers this morning with new ones providing expanded capabilities in the station’s U.S. segment. Whitson was in the Destiny lab module swapping routers while Pesquet was inside the Harmony module performing the computer maintenance. The router swaps and software updates were done to get ready for the arrival of the next station crew.

Image above: This night image from the space station captures sparkling cities and a sliver of daylight framing the northern hemisphere. Image Credit: NASA.

Expedition 51 will expand by two crew members when a veteran Roscosmos cosmonaut and a first time NASA space-flier arrive on Thursday. Soyuz Commander Fyodor Yurchikhin and Flight Engineer Jack Fischer will launch aboard the Soyuz MS-04 spacecraft and take a six-hour, four-orbit ride before docking to the Poisk module. The duo will begin a mission expected to last about 4-1/2 months.

Orbital ATK is getting ready to roll out its Cygnus spacecraft loaded with over 7,600 pounds science gear and crew supplies. Cygnus is scheduled to launch Tuesday at 11:11 a.m. and take a four-day delivery trip before being captured by the Canadarm2 and installed to the Unity module.

NASA’s partnership in a future European Space Agency (ESA) mission to Jupiter and its moons has cleared a key milestone, moving from preliminary instrument design to implementation phase.

Designed to investigate the emergence of habitable worlds around gas giants, the JUpiter ICy Moons Explorer (JUICE) is scheduled to launch in five years, arriving at Jupiter in October 2029. JUICE will spend almost four years studying Jupiter’s giant magnetosphere, turbulent atmosphere, and its icy Galilean moons—Callisto, Ganymede and Europa.

The April 6 milestone, known as Key Decision Point C (KDP-C), is the agency-level approval for the project to enter building phase. It also provides a baseline for the mission’s schedule and budget. NASA’s total cost for the project is $114.4 million. The next milestone for the NASA contributions will be the Critical Design Review (CDR), which will take place in about one year. The CDR for the overall ESA JUICE mission is planned in spring 2019.

“We’re pleased with the overall design of the instruments and we’re ready to begin implementation,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. “In the very near future, JUICE will go from the drawing board to instrument building and then on to the launch pad in 2022.”

JUICE

JUICE is a large-class mission—the first in ESA’s Cosmic Vision 2015-2025 program carrying a suite of 10 science instruments. NASA will provide the Ultraviolet Spectrograph (UVS), and also will provide subsystems and components for two additional instruments: the Particle Environment Package (PEP) and the Radar for Icy Moon Exploration (RIME) experiment.

The UVS was selected to observe the dynamics and atmospheric chemistry of the Jovian system, including its icy satellites and volcanic moon Io. With the planet Jupiter itself, the instrument team hopes to learn more about the vertical structure of its stratosphere and determine the relationship between changing magnetospheric conditions to observed auroral structures. The instrument is provided by the Southwest Research Institute (SwRI), at a cost of $41.2 million.

The PEP is a suite of six sensors led by the Swedish Institute of Space Physics (IRF), capable of providing a 3-D map of the plasma system that surrounds Jupiter. One of the six sensors, known as PEP-Hi, is provided by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, and is comprised of two separate components known as JoEE and JENI. While JoEE is focused primarily on studying the magnetosphere of Ganymede, JENI observations will reveal the structure and dynamics of the donut-shaped cloud of gas and plasma that surrounds Europa. The total cost of the NASA contribution to the PEP instrument package is $42.4 million.

The Radar for Icy Moon Exploration (RIME) experiment, an ice penetrating radar, which is a key instrument for achieving groundbreaking science on the geology, is led by the Italian Space Agency (ASI). NASA’s Jet Propulsion Laboratory (JPL), in Pasadena, California, is providing key subsystems to the instrument, which is designed to penetrate the surface of Jupiter's icy moons to learn more about their subsurface structure. The instrument will focus on Callisto, Ganymede, and Europa, to determine the formation mechanisms and interior processes that occur to produce bodies of subsurface water. On Europa, the instrument also will search for thin areas of ice and locations with the most geological activity, such as plumes. The total cost of the NASA contribution is $30.8 million.

How will JUICE complement NASA’s Europa Clipper multiple flyby mission, also scheduled to launch in the early 2020s?

“The missions are like close members of the same family. Together they will explore the entire Jovian system,” said Curt Niebur, program scientist at NASA Headquarters. “Clipper is focused on Europa and determining its habitability. JUICE is looking for a broader understanding how the entire group of Galilean satellites formed and evolved.”

Niebur says by examining the complexity of the Jupiter system, we will learn more about how habitable areas form in our solar system and beyond. “We’ve learned that habitable environments can arise in surprising places and in unexpected ways. Life may not be limited to the surface of Earth-like worlds orbiting at just the right distance from their suns.”

These raw, unprocessed images of Saturn's moon, Atlas, were taken on April 12, 2017, by NASA's Cassini spacecraft. The flyby had a close-approach distance of about 7,000 miles (11,000 kilometers).

These images are the closest ever taken of Atlas and will help to characterize its shape and geology. Atlas (19 miles, or 30 kilometers across) orbits Saturn just outside the A ring -- the outermost of the planet's bright, main rings.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency's Science Mission Directorate in Washington. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colorado. Caltech in Pasadena manages JPL for NASA.

Holden Crater was once filled by at least two different lakes. The sediments deposited in those lakes are relatively light-toned where exposed, as seen in this observation from NASA's Mars Reconnaissance Orbiter.

Each layer represents a different point in time and perhaps a changing environment for Martian life, if it existed. The elongated ridges with sharp crests are sand dunes.

The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25.9 centimeters (10.2 inches) per pixel (with 1 x 1 binning); objects on the order of 78 centimeters (30.7 inches) across are resolved.] North is up.

Although galaxy formation and evolution are still far from being fully understood, the conditions we see within certain galaxies — such as so-called starburst galaxies — can tell us a lot about how they have evolved over time. Starburst galaxies contain a region (or many regions) where stars are forming at such a breakneck rate that the galaxy is eating up its gas supply faster than it can be replenished!

NGC 4536 is such a galaxy, captured here in beautiful detail by the Hubble’s Wide Field Camera 3 (WFC3). Located roughly 50 million light-years away in the constellation of Virgo (The Virgin), it is a hub of extreme star formation. There are several different factors that can lead to such an ideal environment in which stars can form at such a rapid rate. Crucially, there has to be a sufficiently massive supply of gas. This might be acquired in a number of ways — for example by passing very close to another galaxy, in a full-blown galactic collision, or as a result of some event that forces lots of gas into a relatively small space.

Star formation leaves a few tell-tale fingerprints, so astronomers can tell where stars have been born. We know that starburst regions are rich in gas. Young stars in these extreme environments often live fast and die young, burning extremely hot and exhausting their gas supplies fairly quickly. These stars also emit huge amounts of intense ultraviolet light, which blasts the electrons off any atoms of hydrogen lurking nearby (a process called ionization), leaving behind often colorful clouds of ionized hydrogen (known in astronomer-speak as HII regions).

jeudi 13 avril 2017

Commander Peggy Whitson and Flight Engineers Thomas Pesquet and Oleg Novitskiy juggled a wide variety of space science and human research Thursday. The Expedition 51 trio also switched roles from orbital scientists to high-flying technicians maintaining the systems of the International Space Station.

Whitson started the day testing her fine motor skills to help researchers understand space adaptation and potentially design future touch-based devices for astronauts. The commander then spent the afternoon on space plumbing and worked on the Water Recovery System that converts urine and sweat into clean drinking water.

Pesquet began his morning observing what happens to materials heated to extreme temperatures. The Electrostatic Levitation Furnace can reveal combustion properties and synthesize materials that are very difficult to produce on Earth. In the afternoon, he studied the different phases of metallic alloys in the Material Science Research Rack.

Novitskiy, who is on his second station mission, worked throughout the day on troubleshooting a computer issue in the Zarya cargo module. Towards the end of the day, he charged computer batteries inside the Soyuz MS-03 spacecraft and flushed water tanks into the Progress 66 cargo craft.

Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other "ocean worlds" in our solar system and beyond. The findings are presented in papers published Thursday by researchers with NASA’s Cassini mission to Saturn and Hubble Space Telescope.

NASA ScienceCasts: Ocean Worlds

Video above: We once thought oceans made our planet unique, but we’re now coming to realize that ‘ocean worlds’ are all around us. Video Credit: NASA.

In the papers, Cassini scientists announce that a form of chemical energy that life can feed on appears to exist on Saturn's moon Enceladus, and Hubble researchers report additional evidence of plumes erupting from Jupiter's moon Europa.

“This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate at Headquarters in Washington. ”These results demonstrate the interconnected nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not.”

Image above: This illustration shows Cassini diving through the Enceladus plume in 2015. New ocean world discoveries from Cassini and Hubble will help inform future exploration and the broader search for life beyond Earth. Image Credits: NASA/JPL-Caltech.

The paper from researchers with the Cassini mission, published in the journal Science, indicates hydrogen gas, which could potentially provide a chemical energy source for life, is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor.

The presence of ample hydrogen in the moon's ocean means that microbes – if any exist there – could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water. This chemical reaction, known as "methanogenesis" because it produces methane as a byproduct, is at the root of the tree of life on Earth, and could even have been critical to the origin of life on our planet.

Life as we know it requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. With this finding, Cassini has shown that Enceladus – a small, icy moon a billion miles farther from the sun than Earth – has nearly all of these ingredients for habitability. Cassini has not yet shown phosphorus and sulfur are present in the ocean, but scientists suspect them to be, since the rocky core of Enceladus is thought to be chemically similar to meteorites that contain the two elements.

Image above: This graphic illustrates how Cassini scientists think water interacts with rock at the bottom of the ocean of Saturn's icy moon Enceladus, producing hydrogen gas. Image Credit: NASA/JPL-Caltech.

"Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth," said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

The Cassini spacecraft detected the hydrogen in the plume of gas and icy material spraying from Enceladus during its last, and deepest, dive through the plume on Oct. 28, 2015. Cassini also sampled the plume's composition during flybys earlier in the mission. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water, about 1 percent is hydrogen and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia.

The measurement was made using Cassini's Ion and Neutral Mass Spectrometer (INMS) instrument, which sniffs gases to determine their composition. INMS was designed to sample the upper atmosphere of Saturn's moon Titan. After Cassini's surprising discovery of a towering plume of icy spray in 2005, emanating from hot cracks near the south pole, scientists turned its detectors toward the small moon.

Cassini wasn't designed to detect signs of life in the Enceladus plume – indeed, scientists didn't know the plume existed until after the spacecraft arrived at Saturn.

"Although we can't detect life, we've found that there's a food source there for it. It would be like a candy store for microbes," said Hunter Waite, lead author of the Cassini study.

Image above: These composite images show a suspected plume of material erupting two years apart from the same location on Jupiter's icy moon Europa. Both plumes, photographed in UV light by Hubble, were seen in silhouette as the moon passed in front of Jupiter. Image Credits: NASA/ESA/STScI/USGS.

The new findings are an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea; the new findings support that conclusion and add that the rock appears to be reacting chemically to produce the hydrogen.

The paper detailing new Hubble Space Telescope findings, published in The Astrophysical Journal Letters, reports on observations of Europa from 2016 in which a probable plume of material was seen erupting from the moon’s surface at the same location where Hubble saw evidence of a plume in 2014. These images bolster evidence that the Europa plumes could be a real phenomenon, flaring up intermittently in the same region on the moon's surface.

The newly imaged plume rises about 62 miles (100 kilometers) above Europa’s surface, while the one observed in 2014 was estimated to be about 30 miles (50 kilometers) high. Both correspond to the location of an unusually warm region that contains features that appear to be cracks in the moon’s icy crust, seen in the late 1990s by NASA's Galileo spacecraft. Researchers speculate that, like Enceladus, this could be evidence of water erupting from the moon’s interior.

Image above: The green oval highlights the plumes Hubble observed on Europa. The area also corresponds to a warm region on Europa's surface. The map is based on observations by the Galileo spacecraft. Image Credits: NASA/ESA/STScI/USGS.

“The plumes on Enceladus are associated with hotter regions, so after Hubble imaged this new plume-like feature on Europa, we looked at that location on the Galileo thermal map. We discovered that Europa’s plume candidate is sitting right on the thermal anomaly," said William Sparks of the Space Telescope Science Institute in Baltimore, Maryland. Sparks led the Hubble plume studies in both 2014 and 2016.

The researchers say if the plumes and the warm spot are linked, it could mean water being vented from beneath the moon's icy crust is warming the surrounding surface. Another idea is that water ejected by the plume falls onto the surface as a fine mist, changing the structure of the surface grains and allowing them to retain heat longer than the surrounding landscape.

NASA: Ingredients for Life at Saturn’s Moon Enceladus

For both the 2014 and 2016 observations, the team used Hubble's Space Telescope Imaging Spectrograph (STIS) to spot the plumes in ultraviolet light. As Europa passes in front of Jupiter, any atmospheric features around the edge of the moon block some of Jupiter’s light, allowing STIS to see the features in silhouette. Sparks and his team are continuing to use Hubble to monitor Europa for additional examples of plume candidates and hope to determine the frequency with which they appear.

NASA's future exploration of ocean worlds is enabled by Hubble's monitoring of Europa's putative plume activity and Cassini's long-term investigation of the Enceladus plume. In particular, both investigations are laying the groundwork for NASA's Europa Clipper mission, which is planned for launch in the 2020s.

“If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them,” said Jim Green, Director of Planetary Science, at NASA Headquarters.

Europa Water Vapor Plumes - More Hubble Evidence

Hubble's identification of a site which appears to have persistent, intermittent plume activity provides a tempting target for the Europa mission to investigate with its powerful suite of science instruments. In addition, some of Sparks' co-authors on the Hubble Europa studies are preparing a powerful ultraviolet camera to fly on Europa Clipper that will make similar measurements to Hubble's, but from thousands of times closer. And several members of the Cassini INMS team are developing an exquisitely sensitive, next-generation version of their instrument for flight on Europa Clipper.

For more information on ocean worlds in our solar system and beyond, visit:

Just like a bear after its winter sleep, CERN’s big machines are gradually awakening after the extended year-end technical stop (EYETS). The first beams for 2017 are expected to circulate in the Large Hadron Collider (LHC) in early May, but before that the accelerator complex and all the experiments that it serves have to be put back into operation, one after the other.

In the first week of April, the Linear accelerator 2 (Linac 2), starting point of the protons used in experiments at CERN, successfully accelerated its first proton beam, and made it ready to be sent to the Proton Synchrotron Booster (PSB).

On 10 April, the PSB was also restarted. As the second element of the chain, the PSB increases the energy of the beam received from Linac 2 and sends alternatively it to the Proton Synchrotron (PS) and to the Isotope mass Separator On-Line facility (ISOLDE).

The accelerators awaken. CERN

Video above: The ISOLDE facility has gathered unique expertise in research with radioactive beams. Over 700 isotopes of more than 70 elements have been used in a wide range of research domains, from cutting edge nuclear structure studies, through nuclear astrophysics, to solid state and life sciences. Video Credit: CERN.

The next step is to put the Proton Synchrotron (PS) back in operation on 17 April. It is the oldest accelerator still in service and currently the third component in the accelerator complex. It pushes the beams to even higher energy and sends them to the Super Proton Synchrotron (SPS), last element of the accelerator chain before the LHC. It also feeds the East Area where the Cosmics Leaving Outdoor Droplets (CLOUD) experiment is situated, the Antiproton Decelerator, and the neutron time-of-flight facility (n_TOF).

The accelerators awaken. CERN

Video above: The purpose of n_TOF is to study neutron-nucleus interactions, which play a key role in neutron-related processes, important in a wide range of context, from astrophysics, to hadrontherapy (the treatment of tumors with beams of hadrons), and the development of retreatment of nuclear waste. Video Credit: CERN.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

mercredi 12 avril 2017

NASA scientists are releasing new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night. The clouds and sun glint — added here for aesthetic effect — are derived from MODIS instrument land surface and cloud cover products.

In the years since the 2011 launch of the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite, a research team led by Earth scientist Miguel Román of NASA’s Goddard Space Flight Center has been analyzing night lights data and developing new software and algorithms to make night lights imagery clearer, more accurate and readily available. They are now on the verge of providing daily, high-definition views of Earth at night, and are targeting the release of such data to the science community later this year.

Today they are releasing a new global composite map of night lights as observed in 2016, as well as a revised version of the 2012 map. The NASA group has examined the different ways that light is radiated, scattered and reflected by land, atmospheric and ocean surfaces. The principal challenge in nighttime satellite imaging is accounting for the phases of the moon, which constantly varies the amount of light shining on Earth, though in predictable ways. Likewise, seasonal vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world.

The changing face of our Galaxy is revealed in a new video from ESA’s Gaia mission. The motion of two million stars is traced 5 million years into the future using data from the Tycho-Gaia Astrometric Solution, one of the products of the first Gaia data release. This provides a preview of the stellar motions that will be revealed in Gaia's future data releases, which will enable scientists to investigate the formation history of our Galaxy.

The motion of two million stars

Video above: Two million stars in our Galaxy, with their motions traced five million years into the future. Video Credits: ESA/Gaia/DPAC.

Stars move through our Galaxy, the Milky Way, although the changes in their positions on the sky are too small and slow to be appreciated with the naked eye over human timescales. These changes were first discovered in the eighteenth century by Edmond Halley, who compared stellar catalogues from his time to a catalogue compiled by the astronomer Hipparchus some two thousand years before. Nowadays, stellar motions can be detected with a few years' worth of high-precision astrometric observations, and ESA's Gaia satellite is currently leading the effort to pin them down at unprecedented accuracy.

A star’s velocity through space is described by the proper motion, which can be measured by monitoring the movement of a star across the sky, and the radial velocity, which quantifies the star's motion towards or away from us. The latter can be inferred from the shift towards blue or red wavelengths of certain features – absorption lines – in the star's spectrum.

Launched in 2013, Gaia started scientific operations in July 2014, scanning the sky repeatedly to obtain the most detailed 3D map of our Galaxy ever made. The first data release [1], published in September 2016, was based on data collected during Gaia's first 14 months of observations and comprised a list of 2D positions – on the plane of the sky – for more than one billion stars, as well as distances and proper motions for a subset of more than two million stars in the combined Tycho–Gaia Astrometric Solution, or TGAS.

The TGAS dataset consists of stars in common between Gaia's first year and the earlier Hipparcos and Tycho-2 Catalogues, both derived from ESA's Hipparcos mission, which charted the sky more than two decades ago.

This video shows the 2 057 050 stars from the TGAS sample, with the addition of 24 320 bright stars from the Hipparcos Catalogue that are not included in Gaia's first data release. The stars are plotted in Galactic coordinates and using a rectangular projection: in this, the plane of the Milky Way stands out as the horizontal band with greater density of stars. Brighter stars are shown as larger circles, and an indication of the true colour of each star is also provided; information about brightness and colour is based on the Tycho-2 catalogue from the Hipparcos mission.

The video starts from the positions of stars as measured by Gaia between 2014 and 2015, and shows how these positions are expected to evolve in the future, based on the proper motions from TGAS [2]. The frames in the video are separated by 750 years, and the overall sequence covers 5 million years. The stripes visible in the early frames reflect the way Gaia scans the sky and the preliminary nature of the first data release; these artefacts are gradually washed out in the video as stars move across the sky.

Image above: The location of the Orion constellation (right) and of two stellar clusters (left) in the first frame of the video. Image Credit: ESA/Gaia/DPAC.

The shape of the Orion constellation can be spotted towards the right edge of the frame, just below the Galactic Plane, at the beginning of the video. As the sequence proceeds, the familiar shape of this constellation (and others) evolves into a new pattern. Two stellar clusters – groups of stars that were born together and consequently move together – can be seen towards the left edge of the frame: these are the alpha Persei (Per OB3) and Pleiades open clusters.

Stars seem to move with a wide range of velocities in this video, with stars in the Galactic Plane moving quite slow and faster ones appearing over the entire frame. This is a perspective effect: most of the stars we see in the plane are much farther from us, and thus seem to be moving slower than the nearby stars, which are visible across the entire sky.

Some of the stars appear to dart across the sky with very high velocities: for some stars, this is an effect of their close passage to the Sun – for example, in about 1.35 million years, the star Gliese 710 will pass within about 13 500 au (10 trillion kilometres) from the Sun. Other stars seem to trace arcs from one side of the sky to the other, passing close to the galactic poles, accelerating and decelerating in the process: in fact, this acceleration and deceleration are spurious effects since these stars move with a constant velocity through space.

Stars located in the Milky Way's halo, a roughly spherical structure in which the Galactic Plane is embedded, also appear to move quite fast because stellar motions in the video are calculated with respect to the moving Sun, which is located in the Galactic Plane; however, halo stars move very slowly with respect to the centre of the Galaxy.

Although this visualisation displays only the motion of stars, there is an indication in the first frame of interstellar clouds of gas and dust that block our view of more distant stars. The subsequent sequence of stellar motions shows where each star is expected to be at a given time in the future, but does not track the motion of interstellar clouds. The fact that dark clouds seem to disappear over time is a spurious effect. Similarly, the video does not predict the future positions of stars that are currently hidden by interstellar material and hence have not been observed by Gaia.

After a few million years, the plane of the Milky Way appears to have shifted towards the right: this is mainly the consequence of the motion of the Sun with respect to that of other, nearby stars in the Milky Way. However, the regions that are depleted of stars in the video will not appear as such to future observers looking at the sky from Earth: instead, they will be replenished by stars that are not part of the TGAS sample and therefore not present in this view. The Large and Small Magellanic Clouds, whose stars are not well sampled in the TGAS data, are not visible in this view.

Compiled as a taster to the much larger and more precise catalogue that will be published with Gaia's second data release, TGAS is twice as precise and contains almost 20 times as many stars as the previous definitive reference for astrometry, the Hipparcos Catalogue. As such, it represents a major advance in terms of high precision parallaxes and proper motions.

Scientists across the world have been combining TGAS data with other stellar catalogues assembled using ground-based observations, to obtain larger samples of stars for which positions, distances and proper motions are available. Thus far, three such catalogues have been compiled: the HSOY ("Hot Stuff for One Year") catalogue, which contains the proper motions for 580 million stars, the US Naval Observatory CCD Astrograph Catalog 5 (UCAC 5), listing 100 million proper motions, and the Gaia-PS1-SDSS (GPS1) proper motion catalogue, which includes 350 million proper motions.

Gaia's second data release, in April 2018, will include not only the positions, but also distances and proper motions for over one billion stars, as well as radial velocities for a small subset of them. This will mark a new era in the field of astrometry, enabling scientists to study the past positions of stars – to explore the formation history of our Galaxy – and to predict their future positions to a level of accuracy that was never achieved before.

Notes:

[1] Gaia’s first data release (Gaia DR1) was published on 14 September 2016. This comprised a catalogue of the positions on the sky and the brightness of more than a billion stars – the largest all-sky survey of celestial objects to date – as well as the Tycho-Gaia Astrometric Solution (TGAS), containing the distances and motions for the two million stars in common between the Gaia dataset and the Hipparcos and Tycho-2 catalogues. The TGAS dataset is twice as precise and contains almost 20 times as many stars as the previous definitive reference for astrometry, the Hipparcos Catalogue.

[2] To calculate the future positions of stars, the astrometric measurements from the TGAS dataset were combined with a sample of 235,966 radial velocity measurements from the RAVE, GALAH, and APOGEE catalogues. The calculation is based on a linear extrapolation of the measured velocities of stars, which is a reasonable first-order approximation to study stellar motions on short timescales of millions of years, such as the ones shown in the video; to investigate longer timescales, scientists make use of N-body simulations, a numerical procedure that takes into account the gravity actually experienced by the stars at any time in the past or future.

The moon no longer has a magnetic field, but NASA scientists are publishing new research that shows heat from crystallization of the lunar core may have driven its now-defunct magnetic field some 3 billion years ago.

Magnetized lunar rocks returned to Earth during the Apollo missions established that the moon once had a magnetic field. The moon’s magnetic field lasted for more than a billion years and, at one point, it was as strong as the one generated by modern Earth. Scientists believe that a lunar dynamo -- a molten, churning core at the center of the moon -- may have powered the magnetic field, but previously did not understand how it had been generated and maintained.

In a paper recently published in Earth and Planetary Science Letters, scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Center in Houston argue that this dynamo was caused by crystallization of the lunar core.

“Our work ties together physical and chemical constraints and helps us understand how the moon acquired and maintained its magnetic field — a difficult problem to tackle for any inner solar system body,” said Kevin Righter, the first author of the study and JSC’s high pressure experimental petrology lab lead.

According to the paper, the moon likely had an iron/nickel core with only a small amount of sulfur and carbon, thus giving the lunar core a high melting point. As a result, the lunar core likely started crystallizing early in lunar history, and the heat released by crystallization may have driven an early magnetic field that is recorded in ancient lunar samples.

Full Moon Photographed From Apollo 11 Spacecraft. Image Credit: NASA

“We created several synthetic core compositions based on the latest geochemical data from the moon, and equilibrated them at the pressures and temperatures of the lunar interior,” Righter said.

A magnetic field has been recorded in lunar samples as young as 3.1 billion years old, but is currently inactive, indicating that at some point between then and now, the heat flow declined to a point where the lunar dynamo became inactive. The lunar core is currently thought to be composed of a solid inner and liquid outer core, known from Apollo seismic and other geophysical and spacecraft data. The new specific lunar core composition proposed by the ARES group likely would be partially solid and liquid today, consistent with the seismic and geophysical data.

The ARES scientists prepared powders of iron, nickel, sulfur and carbon based on geochemical proportion estimates of the moon from recent analyses of Apollo samples. Once prepared, the powders were encapsulated and heated under pressures corresponding to those in the lunar interior. Because the moon may have experienced high temperatures in its early history and lower temperatures during later cooling, the scientists investigated a wide range of temperatures.

Detailed compositions and textures of the solids and liquids formed at the higher pressure and temperature conditions were examined.

Before these new results, the conundrum was that modelling of the moon involved an iron/nickel core with sulfur contents so high (and melting point so low) that crystallization would not have occurred until very late in lunar history. Thus the source of the heat flow out of the core required to drive a dynamo was unclear.

Various sources were proposed such as heat from impact or shear forces. The ARES research team acknowledges that such sources may be real, but if the heat from crystallization of the outer core is available, it is a simple and straightforward, source for a lunar dynamo and would fit well with the expected timing.

“The ARES team is excited because this work shows that a specific geochemically-derived composition can explain many geophysical aspects of the lunar core,” says co-author Lisa Danielson.

Image above: This artist's concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B. Image Credits: NASA/JPL-Caltech.

With two suns in its sky, Luke Skywalker's home planet Tatooine in "Star Wars" looks like a parched, sandy desert world. In real life, thanks to observatories such as NASA's Kepler space telescope, we know that two-star systems can indeed support planets, although planets discovered so far around double-star systems are large and gaseous. Scientists wondered: If an Earth-size planet were orbiting two suns, could it support life?

It turns out, such a planet could be quite hospitable if located at the right distance from its two stars, and wouldn't necessarily even have deserts. In a particular range of distances from two sun-like host stars, a planet covered in water would remain habitable and retain its water for a long time, according to a new study in the journal Nature Communications.

"This means that double-star systems of the type studied here are excellent candidates to host habitable planets, despite the large variations in the amount of starlight hypothetical planets in such a system would receive," said Max Popp, associate research scholar at Princeton University in New Jersey, and the Max Planck Institute of Meteorology in Hamburg, Germany.

Popp and Siegfried Eggl, a Caltech postdoctoral scholar at NASA's Jet Propulsion Laboratory, Pasadena, California, created a model for a planet in the Kepler-35 system. In reality, the stellar pair Kepler-35A and B host a planet called Kepler-35b, a giant planet about eight times the size of Earth, with an orbit of 131.5 Earth days. For their study, researchers neglected the gravitational influence of this planet and added a hypothetical water-covered, Earth-size planet around the Kepler-35 A and B stars. They examined how this planet’s climate would behave as it orbited the host stars with periods between 341 and 380 days.

"Our research is motivated by the fact that searching for potentially habitable planets requires a lot of effort, so it is good to know in advance where to look," Eggl said. "We show that it's worth targeting double-star systems."

In exoplanet research, scientists speak of a region called the "habitable zone," the range of distances around a star where a terrestrial planet is most likely to have liquid water on its surface. In this case, because two stars are orbiting each other, the habitable zone depends on the distance from the center of mass that both stars are orbiting. To make things even more complicated, a planet around two stars would not travel in a circle; instead, its orbit would wobble through the gravitational interaction with the two stars.

Popp and Eggl found that on the far edge of the habitable zone in the Kepler-35 double-star system, the hypothetical water-covered planet would have a lot of variation in its surface temperatures. Because such a cold planet would have only a small amount of water vapor in its atmosphere, global average surface temperatures would swing up and down by as much as 3.6 degrees Fahrenheit (2 degrees Celsius) in the course of a year.

Kepler Space Telescope. Image Credit: NASA

"This is analogous to how, on Earth, in arid climates like deserts, we experience huge temperature variations from day to night," Eggl said. "The amount of water in the air makes a big difference."

But, closer to the stars, near the inner edge of the habitable zone, the global average surface temperatures on the same planet stay almost constant. That is because more water vapor would be able to persist in the atmosphere of the hypothetical planet and act as a buffer to keep surface conditions comfortable.

As with single-star systems, a planet beyond the outer edge of the habitable zone of its two suns would eventually end up in a so-called "snowball" state, completely covered with ice. Closer than the inner edge of the habitable zone, an atmosphere would insulate the planet too much, creating a runaway greenhouse effect and turning the planet into a Venus-like world inhospitable to life as we know it.

Another feature of the study's climate model is that, compared to Earth, a water-covered planet around two stars would have less cloud coverage. That would mean clearer skies for viewing double sunsets on these exotic worlds.

This image from NASA's Mars Reconnaissance Orbiter shows a small (0.4 kilometer) mesa, one of several surrounded by sand dunes in Noctis Labyrinthyus, an extensively fractured region on the western end of Valles Marineris.

Heavily eroded, with clusters of boulders and sand dunes on its surface, this layered mesa is probably comprised of sedimentary deposits that are being exhumed as it erodes. The layers themselves are visible as faint bands along the lower left edge of the mesa.

The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. [The original image scale is 20.7 centimeters (19.6 inches) per pixel (with 2 x 2 binning); objects on the order of 158 centimeters (62.2 inches) across are resolved.] North is up.

(Highlights: Week of April 3, 2017) - Three crew members prepared for their return to Earth as NASA announced astronaut Peggy Whitson will extend her stay on the International Space Station by three months. The announcement capped a very productive week of science on orbit.

Whitson began growing another crop of Tokyo Bekana Chinese cabbage for the Veg-03 investigation. The crew is already seeing sprouts. Understanding how plants respond to microgravity is an important step for future long-duration space missions, which will require crew members to grow their own food. Astronauts on the station have previously grown lettuce and flowers in the Veggie facility.

Image above: Crew members on the International Space Station capture spectacular night-time images of Earth from their vantage point 230 miles above the surface of the planet. In this photo, the Canadarm 2 remote-controlled arm extends into the frame and in front of the border of the upper atmosphere. Image Credit: NASA.

Veggie provides lighting and necessary nutrients for plants by using a low-cost growth chamber and planting pillows, which deliver nutrients to the root system. The Veggie pillow concept is a low-maintenance, modular system that requires no additional energy beyond a special light to help the plants grow. It supports a variety of plant species that can be cultivated for fresh food, and even for education experiments.

Crew members have commented that they enjoy space gardening, and investigators believe growing plants could provide a psychological benefit to crew members on long-duration missions, just as gardening is often an enjoyable hobby for people on Earth. Data from this investigation could benefit agricultural practices on Earth by designing systems that use valuable resources such as water more efficiently.

Image above: A tiny sprout of Tokyo Bekana cabbage appears from the center of this plant pillow on board the International Space Station. The vegetable is part of the VEG-03 investigation, looking for efficient ways to grow fresh food in space. Image Credit: NASA.

Just as a special light is used to grow these plants, NASA is investigating changing the lighting on the space station to provide a more productive environment for the crew.

Whitson set up and configured light meter hardware for the Testing Solid State Lighting Countermeasures to Improve Circadian Adaptation, Sleep, and Performance During High Fidelity Analog and Flight Studies for the International Space Station (Lighting Effects) investigation. This investigation tests a new lighting design using light-emitting diodes to replace the fragile fluorescent lights currently used on the space station. Whitson took measurements of various light settings in Node 3 and the U.S. Lab to ensure the LEDs provide enough light to be able to complete science experiments while improving her own cognitive performance.

LEDs are adjustable for intensity and color – the blue, white, or yellow sections of the light spectrum. Scientists and doctors want to determine if the new lights can improve crew sleep cycles and alertness during the day. Besides the potential health benefits, these lights also require less energy to run and are lower in mass, making them a prime candidate for use on future spacecraft. Using these same types of lights on Earth, and subtly adjusting their color temperature during the day may help people be more productive, especially those who work a night shift.

Whitson also ran another round of the Universal Docking Port investigation using the Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) on the space station.

Image above: As the space station orbited overhead, NASA astronaut and golf fan Shane Kimbrough captured this image of Augusta National Golf Course in Georgia during The Masters tournament on April 5, calling it "a tradition unlike any other – even from space!" Image Credits: twitter.com/astro_kimbrough.

Whitson worked on guiding two small, bowling-ball-sized satellites into a rendezvous for the SPHERES-UDP investigation. With the ability to dock and undock, SPHERES provide a test bed to address many of the challenges of combining autonomous spacecraft. Mated spacecraft can assemble complex systems in orbit or combine sensors and actuators for satellite servicing and repurposing missions. The SPHERES enable testing of complex tasks through autonomous decision-making processes and real-time image processing. Development of robotic servicing in space can be applied on Earth, such as in missions to an uncharted ocean floor or the construction and repair of seabed pipelines.

mardi 11 avril 2017

A NASA ER-2 high-altitude plane has taken to the air to complete phase one of the 11-week GOES-16 Field Campaign to ensure NOAA's GOES-16 satellite provides precise satellite measurements, which will improve forecasting.

The mission? Ensure that NOAA’s GOES-16’s Advanced Baseline Imager (ABI) and Geostationary Lightning Mapper (GLM) instruments are “seeing” the same targets as the plane’s instruments.

Why? Because, to put it simply, GOES-16’s data has to be as well-calibrated and accurate as possible—lives depend on it.

Flying out of Palmdale, California, NASA’s ER-2 high-altitude plane and its suite of highly-specialized instruments took to the air over the Sonoran Desert in Mexico (the largest dessert in the Western Hemisphere) and the Mojave Desert in Ivanpah, California on March 23 and 28 to validate GOES-16’s ABI— the satellite’s primary instrument.

The plane made several passes over the large and spatially uniform desert regions, collecting an enormous amount of data and clocking nearly 18 hours of flight time. In a highly-coordinated effort, each time the plane passed over a designated region of desert, scientists used the ABI to perform a series of special north-south scans of the corresponding area.

The plan seems simple enough, right? Collect two sets of data, compare the data, and see how well they match. However, validating a satellite’s imager, especially one as advanced as the ABI, is not so easy.

Before the data from the high-altitude plane and GOES-16’s ABI can be compared and analyzed, scientists must first verify that the plane’s instruments are accurate.

To do this, two teams of scientists took to the desert to collect data using an array of ground sensors during various segments of the plane’s flight. NOAA even enlisted the help of its own NOAA/NASA Suomi NPP satellite.

Phase one of the field campaign was timed so that the polar-orbiting satellite’s path would intersect with the high-altitude flights. By using proven, operational data from the Suomi NPP satellite and measurements gathered by hand in the desert, scientists were able to ensure that their measuring stick, the NASA ER-2 high-altitude plane, is accurate.

The real trick was doing this all at the same time.

What’s next?

With this complex dance of scientists, satellites, and planes complete and data collected, there is still work to do. Scientists are currently analyzing the data from this first phase while simultaneously preparing for the second phase of the field campaign.

On April 11, NASA's ER-2 aircraft will fly from Palmdale, California to Warner Robins Air Force Base in Georgia. From there, the GOES-R team will initiate the next phase which will occur from April 12 to May 18.

Video above: This video shows the view from from the NASA ER-2 high-altitude aircraft cockpit before a flight over the Sonoran Desert coastline during the ABI validation flight on March 23. These flights are conducted in order to validate and calibrate NOAA's GOES-16 satellite. Video Credit: NASA.

During this period the plane will make similar flights over the eastern United States and adjacent oceans to check the data collected by GOES-16’s Geostationary Lightning Mapper instrument. The plane is scheduled to fly in lightning-producing storms over both land and ocean while the satellite monitors them from space.

Previously, during a test flight on March 21, nearly seven hours of data were collected over severe lightning-producing storms east of the San Francisco Bay area. These data were collected simultaneously with ground-based lightning detection networks and a lightning imager on the International Space Station. Similar sensors will be used during phase two to verify the satellite’s data.

NASA ER-2 High-Altitude Airborne Science Aircraf. Image Credit: NASA

NASA successfully launched NOAA's GOES-R satellite at 6:42 p.m. EST on November 19, 2016 from Cape Canaveral Air Force Station in Florida and it was renamed GOES-16 when it achieved orbit. GOES-16 is now observing the planet from an equatorial view approximately 22,300 miles above the surface of the Earth.

GOES-16, one of the GOES-R series of satellites will help meteorologists observe and predict local weather events, including thunderstorms, tornadoes, fog, flash floods, and other severe weather. In addition, GOES-16 will monitor hazards such as aerosols, dust storms, volcanic eruptions, and forest fires and will also be used for space weather, oceanography, climate monitoring, in-situ data collection, and for search and rescue.

Image above: The winter shutdown of the LHC enabled upgrades and maintenance to take place (Image: Maximilien Brice/CERN).

Since the beginning of December, hundreds of people have been busy underground at CERN, working to make important repairs and to upgrade many facilities, across the whole of CERN’s accelerator chain and experiments.

This year the annual shutdown, called the Extended Year End Technical Stop (EYETS) is particularly long, lasting until May 2017, to allow more work to be carried out than in previous years.

At the beginning of the shutdown, the entire machine was drained of its liquid helium to avoid wasting any of the precious element, while important work was done to the LHC’s cryogenics system.

Image above: The new dipole magnet ready to be installed in sector 1-2. The magnet was finally replaced on Monday, 16 January. (Image: CERN).

After removing the helium, scientists and engineers were also able to check the cooling and ventilation, vacuum, electrical and other systems, to make sure they were running properly.

Next, the technical team have had to replace one of the 1232 magnets in the LHC’s ring. Once the magnet was replaced, the team had to carry out many tests at room temperature, triple-checking the magnet was connected properly with no leaks, or deformation.

Also, the Super Proton Synchrotron (SPS) beam dump needed replacing. Beam dumps are radiation-shielded blocks, deep underground, where scientists can choose to send beams that have become degraded so that they can be safely absorbed.

Image above: Researchers re-designed and produced a new beam dump that would allow the SPS to reach its full performance for the 2017 run (Image: Maximilien Brice/ CERN).

Issues with the SPS dump last year had limited the number of particle bunches that could be injected into the Large Hadron Collider (LHC), so it needed to be replaced. A heroic effort was made to re-design and produce a new beam dump, which was finally installed in March and will allow the SPS to reach its full performance again for the 2017 run.

A large part of the shutdown had been identifying and labelling individual cables and removing unnecessary ones in preparation for the many new cables that will be needed for future upgrades.

Over the past few weeks the helium has been re-injected into the system and is being slowly cooled so that the machine can be handed back to the operations teams. From now, the injectors in the accelerator chain are being reawakened.

Timelapse CMS experiment clip 5

Video above: A timelapse video showing the CMS detector closing, as the experiments are now getting ready for the LHC restart in early May (Video: CMS/ CERN).

The experiments also used this time to maintain and improve their machines, including the replacement of the detector’s pixel tracker, at the heart of the experiment. All the experiments are now doing final checks before the caverns close, in time for the LHC to be able to inject the first beam in early May.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.